The fabrication of nickel silicide ohmic contacts to n-type 6H-silicon carbide

This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi_2/SiC structure are formed on N-wells created by N^ + ion implantation into Si-faced p-type 6H-SiC epilayer respectively. NiSi and NiSi_2 films are prepared by annealing the Ni and Si films separately deposited. A two-step annealing technology is performed for decreasing of oxidation problems occurred during high temperature processes. The specific contact resistance \rho _c of NiSi contact to n-type 6H-SiC as low as 1.78\times 10^ - 6\Omega cm^2 is achieved after a two-step annealing at 350~^\circC for 20 min and 950^\circC for 3 min in N_2. And 3.84\times 10^ - 6\Omega cm^2 for NiSi_2 contact is achieved. The result for sheet resistance R_\rm sh of the N^ + implanted layers is about 1210\Omega /\square. X-ray diffraction analysis shows the formation of nickel silicide phases at the metal/n-SiC interface after thermal annealing. The surfaces of the nickel silicide after thermal annealing are analysed by scanning electron microscope.